Thursday, November 18, 2010

The mole is the amount of carbon atoms in 12 grams of carbon. On the other hand, a molar mass is the mass of one mole. For example, a dozen means 12 and so, a mole means 12 grams. Using the periodic table is very necessary for solving these problems. Some examples from using the periodic table is that Iron has an atomic mass of 55.8. Then right away you know that the molar mass of the element is also 55.8g.

Sunday, November 14, 2010

Today, we did experiment 2E. This lab is an indirect measurement of the thickness of a piece of aluminum foil.

There were two formulas involved in this experiment:

Volume of a rectangular solid = length X width X height

Density of a substance = mass / volume

We first took three aluminum foils (15 X15)cm. since the measurement of those square aluminum foils might be off by a little bit, we need to measure the length of two widths and take their average; same as the lengths. Then, we took each aluminum foil to the centigram balance for the measurement of mass.Now that we knew the lengths, widths, mass, and density (2.70 g/cm^3), the height can be calculated.

In this experiment, accuracy and precision are very important.

An ACCURATE measurement is a measurement that is close to the accepted values.

A PRECISE measurement id a reproducible measurement, thus, more precise the measurement is, the more significant digits it has.

Take the average thickness of those three aluminum foils, and calculate experimental error.

The shiny side is slightly better reflector of heat. To keep things cold, put the shiny side on the outside [that will reflect incoming heat]. To keep things warm, face the shiny side inward toward the hot food [to reflect the heat that is trying to escape back into the food].